As of now, "Satanism" is not specifically on the list of religions, but you can claim "Other Religion" (though once you see "the list", you'll be surprised to see what specifically is on that list). However, as you know, you can have your own set of dog tags made with "Satanist" on them (as I have), and even if they are inspected, no one is usually the wiser, and won't force you to change it to "Other Religion" (unless they have "the list").

When I was just recently in Kuwait, as part of my outprocessing from Iraq, I was privy to "the list" because I tried to slyly get them to make me an extra set of what I already owned (i.e. "Satanist"), but there was a double take, and they went up the local chain, who then produced "the list" and they said if I wanted a new set made, it would have to be "Other Religion" (I also attempted this when officially changing my records about 6 months prior in Iraq, but again, no dice).

This could be fought for, but until directed by Central, I would not dare try. I am sure they are well aware of these facts.